Parallel Planet

As they admire the moon, Doraemon sees a slip of paper hanging on the silver grass and finds out Nobita's wish: to become smarter. Turns out Nobita has been teased by his classmates again so Doraemon consoles him by saying that the stars will help Nobita. To impress Nobita, he gives him a Celestial Globe and a Celestial Telescope so he can look outside the universe. As they explore the universe, they somehow find a planet that looks exactly like Earth, except that it (along with Japan) appears in a reverse direction. Doraemon and Nobita gather that a reversed world exists and, believing that their parallel counterparts exist as well, they decide to go there by using a spaceship to go through the Celestial Globe.

In the Parallel Planet, they make their way to their home, walking in the opposite direction to get there. They arrived home, which, like everything in this planet, is completely mirrored horizontally. Doraemon takes out an All-Purpose Mirror for Nobita to inspect his reversed house and they find the window closed with no lights on, although they are unaware that their parallel counterparts didn't make their way to their own planet. A barking cat suddenly pursues them and they seek refuge back in the mountain for the night, while trying to debate whether it was a cat or a dog that was pursuing them.

The next day Doraemon and Nobita return home again to investigate further. Hiding behind a corner, they are surprised to find that Dad and Mom had their roles reversed - Mom is now a male going to work, while Dad is now a female staying home to do the housework - hence concluding that since they're in a parallel world, everything is opposite to the real world. They proceed to enter their room and learn that Nobita in this planet wishes to become a dumb and a foolish person, a wish which is opposite to the actual Nobita. Doraemon and Nobita accidentally wake the Doraemon in this world - with a large bow and eyelashes on - from his nap, and try to escape from the window when Parallel Nobita appeared. Deducing that Doraemon and Nobita must have come from a parallel world to theirs, Parallel Nobita suggests they trade places for a day so he could experience going to school in Nobita's planet, while Nobita goes to school in this planet in Parallel Nobita's skirt. After exchanging clothes, Parallel Nobita and Doraemon go to the actual Earth, while Nobita and Parallel Doraemon stay in parallel Earth.

On his way to school, Nobita also finds out about his friends in the opposite world - Suneo and Gian, both in skirts, had their strengths reversed and Suneo chases after Gian to finish his homework, while Shizuka - now in shorts - tells Suneo that she didn't finish the homework either and suggests they seek Nobita's help. He also learns that he is now the class monitor and has to motion the class to greet the teacher, who still teaches - albeit with a necklace, lipstick and heels on. Back in the actual school, Nobita answers the teacher's question in an intelligent and more detailed manner. This causes both teachers to be concerned for Nobita, especially since the Nobita in the skirt is unable to answer his questions correctly.

Back home, Nobita asks Doraemon a gadget so he can return to the real world, but every time he asks for a gadget from him, each of them is either worn out, broken, or ripped-off from the real gadget of Doraemon such as: the Parallel Time Machine, Somewhere Door, and the Bambooshoot-copter. Doraemon causes Nobita to fall off the window and onto the ground hard. Meanwhile, Nobita learns that Dad had splurged on a dress behind Mom's back, so the former becomes really miserable.

Back in the actual Earth, Gian and Suneo try to beat Nobita up for being too smart at school, but are disgusted when he asks them to do so and change their mind. Shizuka catches up with Nobita on his way home and asks him if they can do the homework together, but Nobita replies that he is busy and walks straight home to pluck weeds in the yard. Nobita then remarks to Doraemon that the real world isn't suitable for him, though Doraemon assures him that Nobita does fine without his help. Meanwhile in parallel Earth, as Doraemon isn't of help to Nobita, the former decides to take him to the actual Doraemon at the mountain using a Flying Cloth (which Doraemon hasn't used it for a long time).

As the sun sets in the east, the actual Doraemon askes the actual Nobita if he likes the Parallel Planet and he agrees. Doraemon replies that there are more plants in the parallel world than the real earth and also tells him that there are more mysteries and unique things to discover and learn from the parallel world. Parallel Nobita and Parallel Doraemon bid farewell to the Nobita and Doraemon as they head back to the real world. However, midway through the flight, Nobita realizes that he forgot to change back clothes with Parallel Nobita before they left the parallel world and he rocks the ship while panicking.